1. Field of the Invention
The present invention relates to an image reading apparatus for automatically feeding an original cassette containing an original to be read, with respect to a subject holder, thereafter rotating and trimming the original cassette, as required, and feeding the original cassette in an auxiliary scanning direction while illuminating light is applied to the original in a main scanning direction thereby to read the original.
2. Prior Art
Image scanning reading and reproducing systems are widely used in the printing and platemaking industries for electrically processing image information of originals or subjects to produce original film plates with a view to simplifying the entire process and improving the quality of printed images.
The image scanning reading and reproducing systems are basically constructed of an image reading apparatus and an image reproducing apparatus. In the image reading apparatus, an original or subject whose image information is to be read is contained in an original cassette, and the original cassette is fed in an auxiliary scanning direction by a subject holder. While the original cassette is being fed in the auxiliary scanning direction, an illuminating light source is energized to apply illuminating light to the original in a main scanning direction substantially normal to the auxiliary scanning direction. Therefore, the image information of the original is two-dimensionally scanned by the illuminating light.
The subject holder is often combined with a mechanism for rotating the original cassette with respect to the subject holder in order to adjust the halftone dot angle or gravure angle of the original, and a mechanism for moving the original cassette in a direction normal to the auxiliary scanning direction of the subject holder in order to trim the original mechanically.
Heretofore, the subject holder has a table movable in trimming directions toward and away from the subject holder and a turntable mounted centrally on the table. The original cassette needs to be manually installed on and detached from the turntable by the operator. Therefore, the procedure for mounting and removing original cassette on and from the turntable is tedious and inefficient, and the entire image reading process cannot be automatized.
If the original cassette were to be automatically fed to the turntable by a feed mechanism, the original cassette would have to be positioned highly accurately and rigidly with respect to the turntable because the original cassette would tend to be positionally displaced when the turntable rotates. The positionally displaced original cassette would not allow the original contained therein to be read accurately.
If the original cassette were to be fed to the turntable by a feed mechanism, the feed mechanism would interfere with the turntable when the turntable is rotated, trimmed, and moved in the auxiliary scanning direction, together with the original cassette, with the result that it would not be able to displace the turntable smoothly in any desired direction. Because of these difficulties, there has not yet been proposed any feed mechanism for automatically feeding the original cassette to the turntable.
In the image reading apparatus, it is sometimes desirable to automatically identify the type of an original or subject contained in the original cassette or the individual identification number of the original cassette. One proposed arrangement for such automatic identification includes a reflective code comprising white and black bars which encode the type of an original and the number of the original cassette, and the reflective code is applied to the original cassette, so that the code will be optically detected by a reflective light sensor.
Reflective codes are fixedly applied to respective original cassettes. Therefore, the original cassettes are dedicated respectively to the types of originals. Accordingly, as many original cassettes as there are the types of originals are required. Furthermore, it is quite difficult for an inexpensive reflective light sensor to be able to detect many types of codes.